Regulating Mammalian Target of Rapamycin To Tune Vaccination-Induced CD8+ T Cell Responses for Tumor Immunity

Abstract

Vaccine strategies aimed at generating CD8⁺ T cell memory responses are likely to show augmented efficacy against chronic challenges like tumor. The abundance in variety of memory CD8⁺ T cells behooves development of vaccine strategies that generate distinct memory responses and evaluate them for tumor efficacy. In this study, we demonstrate the ability of a variety of rapamycin treatment regimens to regulate virus vaccination-induced CD8⁺ T cell memory responses and tumor efficacy. Strikingly, a short course of high-dose, but not low-dose, rapamycin treatment transiently blocks viral vaccination-induced mammalian target of rapamycin activity in CD8⁺ T cells favoring persistence and Ag-recall responses over type 1 effector maturation; however, prolonged high-dose rapamycin administration abrogated memory responses. Furthermore, a short course of high-dose rapamycin treatment generated CD8⁺ T cell memory responses that were independent of IL-15 and IL-7 and were programmed early for sustenance and greater tumor efficacy. These results demonstrate the impact a regimen of rapamycin treatment has on vaccine-induced CD8⁺ T cell responses and indicates that judicious application of rapamycin can augment vaccine efficacy for chronic challenges.